Display device

ABSTRACT

A display apparatus for displaying images and/or data in a vehicle is proposed. The display apparatus encompasses a projection unit and a display surface, the projection unit being arranged on a vehicle roof and/or on a vehicle inside mirror. The display surface is used in particular to display a real image generated by the projection unit.

BACKGROUND OF THE INVENTION

[0001] The invention is based on a display apparatus according to thespecies defined in the main claim. Display apparatuses in vehicles, inwhich a virtual image visible to an observer is generated by the factthat light is projected by a projection unit onto a mirror-coatedsurface, are already known. In this context, a virtual image visible toa viewer is created behind the plane of the mirror. A unit for lightgeneration and projection that is necessary for this purpose isgenerally arranged in the dashboard of the vehicle, i.e. behind thesteering wheel and below the windshield. Vehicle data in particular,e.g. the present vehicle speed, are displayed in such a display. On theone hand the windshield, or on the other hand additional reflectiveelements (called combiners), are used as the reflective surfaces ontowhich the virtual image is projected.

ADVANTAGES OF THE INVENTION

[0002] The display apparatus according to the present invention havingthe features of the principal claim has, in contrast, the advantage thatinstead of the virtual image, a real image is generated. Projection of areal image makes it possible to eliminate the image distortion thatoccurs upon projection of a virtual image, since the real image ispreferably projected directly onto a display surface in a manner visiblefrom several directions. It is particularly advantageous in this contextto arrange a projection apparatus in space-saving fashion on a vehicleroof or on a vehicle inside mirror. It is advantageous here that forprojection of the real image, projection is performed onto a displaysurface outside the windshield, since as a result it is no longernecessary to cover the windshield—which otherwise is merely reflectiveor transparent—with, for example, a light-diffusing film for projectionof the real image. It is moreover particularly advantageous that becausethe projection unit is arranged on the vehicle roof or on the vehicleinside mirror, there is no need for model-specific configuration of thevehicle dashboard with a receptacle for a projection unit in thedashboard unit.

[0003] The features set forth in the dependent claims make possibleadvantageous developments and improvements of the display apparatusdescribed in the main claim. It is particularly advantageous to arrangea structural pattern on the display surface. This structural patterncauses the light directed onto the display surface to be directed in apreferred direction. This preferred direction is generally the viewingdirection of a viewer, for example a driver of the vehicle. The powerlevel of the light radiated onto the display surface can thereby bedecreased with no change in the reading brightness. Targeted lightdeflection can moreover, for example, prevent dazzling of oncomingtraffic or of a passenger.

[0004] It is furthermore advantageous to arrange adjacently to thedisplay surface a reflective surface that serves to display a virtualimage. Projection of the image onto the windshield can thereby beaccomplished as applicable. This is advantageous in particular if animage superimposed on the road scene is to be displayed on thewindshield.

[0005] It is furthermore advantageous to configure the display surfacewith a roughened surface, since this makes possible good legibility ofthe real image if the roughening has sufficient grain.

[0006] It is furthermore advantageous to embody the display surface witha holographically introduced structure, which makes possible efficient,low-loss light deflection.

[0007] It is furthermore advantageous to arrange on the display surfacea surface having a prism structure and/or sawtooth structure, with whichthe light can efficiently be deflected in a selected direction.

[0008] It is furthermore advantageous to embody the display surface as afirst and a second surface portion, in which context light can bedeflected to a first viewer by way of the first surface portion and to asecond viewer by way of the second surface portion, so that it ispossible for two viewers of the display apparatus to view differentimages. For example, while a second viewer is viewing an entertainmentprogram, information about the vehicle, e.g. the vehicle speed or enginespeed, is being displayed to a first viewer, for example the driver.

[0009] It is furthermore advantageous to equip the projection unit witha laser beam generation unit and to generate an image by way of laserbeams, a deflection of the laser beams being accomplished preferablywith mirrors. A bright real image can thereby be generated. It is alsopossible to dispense with a lens optical system for image generation andprojection in the projection unit.

[0010] It is furthermore advantageous to provide the projection pathapproximately parallel to the windshield, since in a region close to thewindshield the light path generally is not interrupted by a user of thevehicle.

DRAWINGS

[0011] Exemplary embodiments of the invention are depicted in thedrawings and explained in more detail in the description which follows.

[0012] In the drawings:

[0013]FIG. 1 shows a first embodiment of a display apparatus in avehicle.

[0014]FIG. 2 shows a further exemplary embodiment of a display apparatusaccording to the present invention.

[0015]FIG. 3 shows an arrangement of various electronic elements of adisplay apparatus according to the present invention.

[0016]FIG. 4 shows a first exemplary embodiment of a projection unitaccording to the present invention.

[0017]FIG. 5 shows a further exemplary embodiment of a projection unitaccording to the present invention.

[0018]FIGS. 6a and 6 b show a first exemplary embodiment of aconfiguration according to the present invention of a display surface.

[0019]FIGS. 7a and 7 b show a further exemplary embodiment of a displaysurface according to the present invention.

[0020]FIG. 8a shows an exemplary embodiment of a configuration accordingto the present invention of a virtual image.

[0021]FIG. 8b shows an exemplary embodiment of a configuration of anouter surface of the display surface.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0022] The display apparatus according to the present invention can beused to display a variety of images and data in a vehicle. In additionto vehicle parameters such as, for example, engine speed, vehicle speed,and/or the ambient temperature of the vehicle, it is also possible todisplay the image from a camera, e.g. the image from a rear or sidecamera as well as the image from an infrared camera. Display of theimage acquired by the infrared camera, in particular, allows a vehicleuser to obtain a good overview of the road even when visibilityconditions are poor, e.g. in fog or darkness. In addition, the displayapparatus can also serve as an output unit of a navigation apparatus fordisplay of a route to be traveled. In a preferred embodiment, a displaysurface is arranged at least in the vicinity of the windshield, and isreadable by a driver of the vehicle and by a passenger. Also possible isan arrangement of a display apparatus according to the present inventionin such a way that a passenger who is not in the first row of seats ofthe vehicle can read the display, for example by the fact that a displaysurface is arranged directly in front of a user's seat. All that isnecessary for this purpose is to provide a corresponding projection unitfor that display surface at a suitable location on the vehicle roof.

[0023]FIG. 1 shows a first exemplary embodiment in which a projectionunit 1 is arranged on a vehicle roof 2. A display surface 4 is arrangedon a mount 5 on an instrument panel 3. A light beam 6 that is radiatedfrom projection unit 1 to display surface 4 is deflected by displaysurface 4 in the direction of a user, as depicted by an arrow 7.Instrument panel 3 is adjacent one on side to a windshield 8 thatextends from instrument panel 3 to vehicle roof 2. Instrument panel 3encloses a dashboard (not shown in further detail in FIG. 1) of thevehicle. A steering wheel 9 is also arranged on instrument panel 3.

[0024] In a preferred exemplary embodiment, projection unit 1 is mountedimmovably on vehicle roof 2. A voltage supply line and a data line,through which the image data to be displayed are transmitted toprojection unit 1, are not depicted in FIG. 1. In a preferred exemplaryembodiment, the voltage supply line and the data line are integratedinto vehicle roof 2 in a manner not visible to a user, and are guidedout of the vehicle roof through a door frame. Light beam 6 that passesfrom projection unit 1 to display surface 4 extends approximatelyparallel to windshield 8. A driver generally does not reach into thisregion, so that light beam 6 is not interrupted by the driver. In afirst exemplary embodiment, display surface 4 is embodied as a diffusingdisplay surface, which is constituted e.g. by roughening an outersurface of a transparent plastic material. Display surface 4 is a highlyreflective surface that is as white as possible and, in a firstexemplary embodiment, is covered with a surface material that exhibitsapproximately the properties of a Lambert radiator. In a preferredexemplary embodiment, display surface 4 is constituted by a suitablefilm that is applied onto mount 5. Mount 5 is moreover adjustable as toits angle of inclination, so that the direction of the observer (arrow7) can be set by tilting mount 5 to the observer's eye level. In afurther preferred exemplary embodiment, display surface 4 is coveredwith a film that allows directed emission of the light. This preventslight from being emitted, for example, toward the windshield.

[0025]FIG. 2 depicts a further exemplary embodiment of a displayapparatus according to the present invention. Here and hereinafter,identical reference characters designate identical elements. In theexemplary embodiment depicted in FIG. 2, a projection unit 10 isarranged on an inside mirror 11. A mirror surface 12 of inside mirror 11is arranged on a side of inside mirror 11 facing away from windshield 8.Mirror surface 12 conceals projection unit 10 from a user as completelyas possible, so that projection unit 1 is not visible to a user of thevehicle and thus is not intrusive.

[0026]FIG. 3 depicts an electrical circuit of a display apparatusaccording to the present invention. Signals of a video camera 21 andfrom vehicle sensors 22 are acquired by a control unit 20. The signalsof video camera 21 and vehicle sensors 22 are processed in control unit20 and forwarded for display to an image processing unit 23. In apreferred exemplary embodiment, image processing unit 23 has a digitalfiltration and calculation unit 24 with which the image signals acquiredby video camera 21 are optionally digitally processed, and with whichthe vehicle variables ascertained by vehicle sensors 22, e.g. vehiclespeed, engine speed, and/or outside temperature, are converted into avisual depiction. Image processing unit 23 furthermore has an activationunit 25 that transmits image data to projection unit 1 and controlsprojection unit 1. In a preferred exemplary embodiment, video camera 21is arranged behind a radiator grille at the front end of the vehicle,thus making possible unobtrusive observation of the area in front of thevehicle. In a further exemplary embodiment, video camera 21 is arrangedin the interior of the vehicle, preferably in the region of the insidemirror, so that observation of the road is performed from the interiorof the vehicle. Vehicle sensors 22 are arranged in the vehicle atsuitable points provided therefor. In a preferred exemplary embodiment,control unit 20 and image processing unit 23 are arranged in thedashboard of the vehicle or in vehicle roof 2. In a preferred exemplaryembodiment, video camera 21 is embodied as an infrared camera, withwhich image acquisition is possible even in poor visibility conditionssuch as darkness and/or fog.

[0027]FIG. 4 depicts a first exemplary embodiment of a projection unit1. A first laser unit 31, a second laser unit 32, and a third laser unit33 are arranged in a housing 30. First laser unit 31 produces red light,second laser unit 32 green light, and third laser unit 33 blue light. Ina preferred exemplary embodiment, the laser units are embodied assemiconductor lasers or solid-state lasers. A first laser beam 41 offirst laser unit 31 can be emitted onto a first mirror 51, with whichfirst laser beam 41 is deflected toward display surface 4. Similarly,second laser beam 42 can be directed onto a second mirror 52, and thirdlaser beam 43 onto a third mirror 53. Mirrors 51, 52, 53 are modifiable,preferably via piezoelements, in terms of their angle of inclination intwo spatial directions about rotation axes lying in the plane of therespective mirror, so that scanning of display surface 4 by laser beams41, 42, and 43 is ensured by means of the mirrors. The use of the threecolors red, green, and blue allows generation of a color image. In anexemplary embodiment that is not depicted in the drawings, instead ofthe three laser units 31, 32, 33 shown in FIG. 4 it is also possible touse only one laser unit of one specific color. This makes possible amonochrome display in the specific color. In a further exemplaryembodiment not depicted in the drawings, light deflection isaccomplished with a micromechanical mirror display (DMA=digital mirrordisplay).

[0028]FIG. 5 shows a further exemplary embodiment of a projection unitaccording to the present invention. A light source 44 preferablyemitting white light, e.g. a halogen light source, is arranged in ahousing 40. The light of light source 44 can be emitted through a liquidcrystal cell 45 and through a lens 46 toward display 4. Liquid crystalcell 45 comprises individual image points whose light transmission canbe influenced by an electrical activation system (not shown in FIG. 3).By appropriate activation of the image points, an image can be generatedby liquid crystal cell 45. The spacing between liquid crystal cell 45and lens 46 is selected, in conjunction with the focal length of lens46, in such a way that the image generated by liquid crystal cell 45 isimaged onto display surface 4. Both the projection unit shown in FIG. 4and that shown in FIG. 5 can be used as a projection unit 1 on thevehicle roof or as a projection unit 10 on an inside mirror.

[0029] In a first embodiment, display surface 4 is configured as a flatsurface. In an exemplary embodiment not depicted in the drawings,display surface 4 can be protected from soiling or damage by a fold-downcover. FIGS. 6a and 6 b show a further exemplary embodiment of asemi-spherical display surface 50. Semi-spherical display surface 50 isembodied as a semi-spherical elevation above instrument panel 3. FIG. 6ashows a view from the direction of the viewer at the height ofinstrument panel 3. FIG. 6b shows a plan view onto semi-sphericaldisplay surface 50 from the position of projection unit 1 or 10. Thesemi-spherical configuration makes possible display of an image over awide spatial angle. As a result, an image can be seen both by a driverof the vehicle and by a passenger. It is moreover also possible for apassenger sitting farther back in the vehicle to read fromsemi-spherical surface 50, which preferably is covered with alight-diffusing film or a light-diffusing layer. To ensure that thesemi-spherical configuration does not result in distortion of thedisplayed image, in a preferred exemplary embodiment a priorcomputational distortion of the image, in which projection ontosemi-spherical display surface 50 is taken into account, is accomplishedin image processing unit 23.

[0030] In FIGS. 7a and 7 b, a display surface is divided into a firstsurface portion 61 and a second surface portion 62. FIG. 7a shows a viewonto surface portions 61 and 62 from a viewer's height corresponding tothe height of instrument panel 3. FIG. 7b shows a plan view from theposition of projection unit 1 or 10.

[0031] An image for a driver can be projected onto first surface portion61, and an image for a passenger onto second surface portion 62, so thatdifferent images can be displayed for the driver and the passenger. Inaddition to an embodiment of surface portions (depicted in FIGS. 7a and7 b) having a triangular base outline, it is also possible to providesurface portions having a rectangular or trapezoidal display surface, orto space the surface portions apart.

[0032]FIG. 8a depicts a further exemplary embodiment of a displayapparatus according to the present invention in which the imageprojected onto a display surface 4 is deflected by display surface 4toward windshield 8. A semi-reflective layer 70, with which light isdeflected toward observer 7, is provided on windshield 8. Reflectiononto semi-reflective layer 70 creates for an observer a virtual imagethat appears to an observer to be located on the side of windshield 8facing away from the observer. It is also possible to use a layer thatreflects, and deflects to an observer, only light of a definedpolarization direction of light beam 6 that is reflected from displaysurface 4. A polarization direction of the light emitted from projectionunit 1 or 10 must, in this context, be adapted to the polarizationdirection of the semi-reflective layer, or vice versa. In an exemplaryembodiment not depicted in FIG. 8a, it is also possible to dispenseentirely with a semi-reflective layer and to generate an image solely byway of a reflection at windshield 8. In the exemplary embodimentdepicted in FIG. 8a, display surface 4 is embodied so as to deflect asmuch light as possible directly toward reflective surface 70, and aslittle light as possible directly to an observer, in order to achievethe brightest possible virtual image. The display surface can have alight-diffracting, light-refracting, reflective, or light-diffusingstructure, as well as a combination of said structures.

[0033]FIG. 8b depicts a preferred exemplary embodiment of such astructure. A light beam 6 strikes display surface 4, which isconstituted by a first layer 81 and a second layer 82. The boundarysurface between first layer 81 and second layer 82 is formed by sawtoothshapes 83. As a result of differently selected refractive indices, totalreflection of light beam 6 at the boundary surface between first layer81 and second layer 82 occurs at an interface from first layer 81 tosecond layer 82. This makes possible directed light deflection toward aviewer or, depending on the orientation of sawtooth shapes 83, towardreflective layer 70. First layer 81 and second layer 82 are preferablymade from a plastic material. In a preferred exemplary embodiment, thestructure is introduced into second layer 82 holographically, e.g. bymeans of laser light. Instead of the sawtooth shapes shown in FIG. 8b,symmetrically configured prisms or other structures are also possible,for example an embodiment as a Fresnel lens. In a further exemplaryembodiment, prism or sawtooth shapes can also be applied onto an outersurface of a display surface by injection molding.

What is claimed is:
 1. A display apparatus in a vehicle, having aprojection unit (1, 10) and having a display surface (4), the projectionunit (1, 10) being arranged on a vehicle roof (2) and/or on an insidemirror (11) of the vehicle, wherein a real image is able to be projectedby the projection unit (1, 10) onto the display surface (4).
 2. Thedisplay apparatus as defined in claim 1, wherein the display surface (4)is arranged on the vehicle in addition to a windshield (8), preferablyadjacent to the windshield on an instrument panel (3) of the vehicle. 3.The display apparatus as defined in one of the foregoing claims, whereina structural pattern (83) is arranged on the display surface (4); andprojected light can be deflected by the structural pattern (83).
 4. Thedisplay apparatus as defined in claim 3, wherein the projected light canbe deflected in the direction of a viewer (7).
 5. The display apparatusas defined in claim 3, wherein a reflective surface (70) is arrangedadjacent to the display surface (4); and the projected light can bedeflected onto the reflective surface (70).
 6. The display apparatus asdefined in one of claims 3 through 5, wherein the structural pattern isconfigured as a roughening of the display surface.
 7. The displayapparatus as defined in one of claims 3 through 6, wherein a layer (82)having a holographically introduced structure is arranged on the displaysurface (4).
 8. The display apparatus as defined in one of claims 3through 7, wherein an outer surface (81) having a prism structure and/ora sawtooth structure (83) is arranged on the display surface (4).
 9. Thedisplay apparatus as defined in one of the foregoing claims, wherein thedisplay surface (50) is of semi-spherical configuration.
 10. The displayapparatus as defined in one of the foregoing claims, wherein a firstimage can be projected onto a first surface portion (61) of the displaysurface; and a second image can be projected onto a second surfaceportion (62) of the display surface.
 11. The display apparatus asdefined in one of the foregoing claims, wherein the projection unit (1,10) is a video projector.
 12. The display apparatus as defined in one ofthe foregoing claims, wherein a light source of the projection unit is alaser beam generation unit (31, 32, 33).
 13. The display apparatus asdefined in claim 12, wherein movable mirrors (51, 52, 53) are arrangedin the projection unit (1, 10); and the light of the laser beamgeneration unit (31, 32, 33) can be deflected by the movable mirrors(51, 52, 53).
 14. The display apparatus as defined in one of theforegoing claims, wherein multiple light sources (31, 32, 33) ofdifferent colors are arranged in the projection unit.
 15. The displayapparatus as defined in one of the foregoing claims, wherein the path ofthe projected light from the projection unit (1, 10) to the displaysurface (4) is at least approximately parallel to a windshield (8) ofthe vehicle.